IP subnetting exercise. By Reem Al-Kanhal

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1 IP subnetting exercise By Reem Al-Kanhal

IP Address : Has two portions: One is network address. Network address is like an area code of telephone number. The other is host address. Network address starts from the left most.

2 IP Address : Has two portions: One is network address. Network address is like an area code of telephone number. The other is host address. Network address starts from the left most. The rest is the host address. Things to memorize: In order to get the number of networks: 2 ^ (Number of bits in the network portion) In order to get the number of host IP Addresses in each subnet: 2 ^ (Number of bit sin the host portion) Network Address is the first IP Address of the network. Broadcast Address is the last IP Address of the network. We can t use those two IP Addresses for any device. Those two IP Addresses are reserved!!! IP Address Scheme: Class A: ~ Subnet mask is What is the number of networks in Class A address? 2 ^ 8 = 256 What is the number of hosts in each of Class A network? 2 ^ 24 = Class B: ~ Subnet mask is What is the number of networks in Class B address? 2 ^ 16 = What is the number of networks in Class B address? 2 ^ 16 = 65536

Class C: 192.0.1.0 ~ 223.255.254.255 Subnet mask is 255.255.255.0. 11111111.11111111. 11111111.00000000 What is the number of networks in Class C address?

3 Class C: ~ Subnet mask is What is the number of networks in Class C address? 2 ^ 24 = What is the number of networks in Class C address? 2 ^ 8 = 256 Class D: ~ Subnetting Subnetting is the process of creating the smaller, and more subnets by borrowing bits from the host portion. borrowing happens from the left most bits of the host portion.

4 Class C Address subnetting: is the class C network address. Subnet mask will be which is Now let s borrow 3 bits from which is host portion. So the subnet mask will be (3 bits borrowed) So what differences have we made??? Condition. 1. we borrowed 3 bits from the host portion. Subnet mask is now We borrowed 3 bits for the network address, so we should have more networks. Time to apply the formula. Number of Networks created by borrowing three bits from host portion: Number of bits borrowed => 3. Number of networks created => 2 ^ (3) = 8. Which means that we have 8 more subnets under the last octet of the IP Address. Number of hosts in each subnet: Number of bits left in the host portion => 5. Number of hosts in each subnet => 2 ^ (5) = 32. Which means that we have 32 hosts in each subnet. We have 8 subnets and each of them has 32 hosts in it. Number of Networks Number of bits borrowed => 3. 2 ^ (3) = 8. We have 8 more subnets. Number of hosts in each subnet Number of bits left in the host portion => 5. 2 ^ (5) = 32. There are 32 hosts in each subnet. Network, and Broadcast Address of the subnet 6 is Network Address Broadcast Address We can t use those two reserved IP Addresses. So the number of the USABLE IP address will be { 2 ^ (no. of host bits) } 2 = 30.

5 First subnet Subnet 0 Second subnet Subnet 1 Third subnet Subnet 2 Forth subnet Subnet 3 Fifth subnet Subnet 4 Sixth subnet Subnet 5 Seventh subnet Subnet 6 Eighth subnet Subnet 7 Range of each subnet ~ / ~ / ~ / ~ / ~ / ~ / ~ / ~ / 27 QUESTION!!! You have Class C network Address. Create subnets by borrowing 4 bits from the host portion. Write down the list of subnets that you created.

6 Class B network subnetting: is the class B network. Subnet mask will be which is Now let s borrow 3 bits from which is the host portion. So the subnet mask will be (3 bits borrowed) So what differences have we made??? Condition. 1. we borrowed 3 bits from the host portion. Subnet mask is now We borrowed 3 bits for the network address, so we should have more networks now. Time to apply the magic formula. Number of Networks Number of bits borrowed => 3. 2 ^ (3) = 8. Which means that we have 8 more subnets under the third octet of the IP Address. Number of hosts in each subnet. Number of bits left in the host portion of the third octet=>. 2 ^ (13) = Each subnet has 8192 hosts. Number of Networks Number of bits borrowed => 3. 2 ^ (3) = 8. Network, and Broadcast Address of the subnet 6 is Network Address Broadcast Address the number of the USABLE IP for each subnet is 2 ^ (no. of host bits) 2 = { 2 ^ (13) } 2 = 8190

7 Range of each subnet First subnet ~ / 19 Second subnet ~ / 19 Third subnet ~ / 19 Forth subnet ~ / 19 Fifth subnet ~ / 19 Sixth subnet ~ / 19 Seventh subnet ~ / 19 Eighth subnet ~ / 19 QUESTION!!! You have Class B network Address, Create subnets by borrowing 3 bits from the host portion. Write down the list of subnets that you created.

Address Class (Exercise) B A

Address Class (Exercise) B A Address Class (Exercise) Address Class 177.100.18.4 B 119.18.45.0 A 192.249.234.191 C 10.10.251.12 A 223.32.232.190 C 129.132.24.2 B 18.250.1.1 A 150.10.15.0 B 197.14.2.0 C 174.17.9.1 B 148.17.9.1 B 193.42.1.1